Packet-based communication systems allow the user of a device, such as a personal computer, to communicate across a computer network such as the Internet, in which case the packet protocol may be Internet Protocol (IP). Packet-based communication systems can be used for video communications. These systems are beneficial to the user as they are often of significantly lower cost than fixed line or mobile networks. This may particularly be the case for long-distance communication. To use a packet-based system, the user must install and execute client software on their device. The client software provides the packet-based connections as well as other functions such as registration and authentication. In addition to video communication, the client may also provide further features such as instant messaging, voice calls, voicemail and file transfer.
One type of packet-based communication system uses a peer-to-peer (“P2P”) topology built on proprietary protocols. To enable access to a peer-to-peer system, the user must execute P2P client software provided by a P2P software provider on their computer, and register with the P2P system. When the user registers with the P2P system the client software is provided with a digital certificate from a server. Once the client software has been provided with the certificate, communication can subsequently be set up and routed between users of the P2P system without the further use of a server. In particular, the users can establish their own communication routes through the P2P system based on the exchange of one or more digital certificates (or user identity certificates, “UIC”), which enable access to the P2P system. The exchange of the digital certificates between users provides proof of the users' identities and that they are suitably authorised and authenticated in the P2P system. Therefore, the presentation of digital certificates provides trust in the identity of the user. It is therefore a characteristic of peer-to-peer communication that the communication is not routed using a server but directly from end-user to end-user. Further details on such a P2P system are disclosed in WO 2005/009019.
In a video communication system such as a packet-based P2P system, during a video call, a first user's terminal will receive video data from a second user's terminal. This received video data typically comprises real-time video of the second user's face or body during the call. The received video data will typically be displayed in a main video area of a display on the first user's terminal.
The first user's terminal will also generate video data to send to the second user. This locally generated data typically comprises real-time video of the first user's face or body.
In addition to the received video displayed in the main area, the first user may also want to be able to view the locally generated video, i.e. the video of themselves which is being transmitted. Thus the first user's own video may be displayed back to them in another smaller video area on the display of their terminal. This is sometimes referred to as the “preview area”, “preview image” or “preview video”.